#include <bits/stdc++.h>

using namespace std;
const int MAXW = 10105;
const int MAXN = 1005;

int dp[MAXN][2];
int V[MAXN];

int main() {
  int N;
  scanf("%d", &N);

  for (int i = 0; i < N; ++i) scanf("%d", &V[i]);

  for (int i = 0; i < N; ++i) {
    dp[i + 1][1] = max(dp[i + 1][1], dp[i][0] + V[i]);
    dp[i + 1][0] = max(dp[i + 1][0], dp[i][1]);
    dp[i + 1][0] = max(dp[i + 1][0], dp[i][0]);
  }

  printf("%d\n", max(dp[N][0], dp[N][1]));
  return 0;
}